Infertility is a major problem in the United States with nearly one out of every five married couples affected. Our knowledge in this area is limited and there is a great need for further research. This project proposes to conduct a systematic and in-depth study of the natural processes of human infertility and fertility. It will study a promising new technique which involves the observation and recording of the cervical mucus discharge which appears at the vulva when estrogen levels increase during the immediate pre-ovulatory phase of the menstrual cycle. Recent research indicates that the cervical mucus PEAK DAY is the most precise clinical sign of ovulation. The new technique is simple, safe, non-invasive and reproducible. The study will be undertaken in two parts using a standardized system of observing for the mucus and recording it. In the first part of the study, a study group of patients who have infertility with abnormalities in cervical mucus discharge will be studied endocrinologically and compared to a similarly studied control group of women with exhibited normal fertility and normal mucus cycles. The evaluation will use radioimmunoassay for measuring serum hFSH, hLH, estradiol - 17 beta, progesterone prolactin and a profile of androgens. In addition, ultrasound will be used to measure the growth and development of the follicles in the two groups. The second portion of the study involves the study of the statistical parameters of the cervical mucus cycle in 20,000 menstrual cycles. This portion of the study is designed to give needed information on the characteristics of the mucus cycle in infertility patients and patients in different reproductive categories. The two portions of the study are inter-related and designed to run concurrently.